The present disclosure is related to an objective lens for endoscopes and to an endoscope equipped with the objective lens for endoscopes.
Conventionally, there is demand for high quality images to be obtained at deep observation depths, in the field of endoscopic observation. Objective lenses for endoscopes in which focus adjustment is possible have been proposed in order to meet this demand. For example, Japanese Unexamined Patent Publication No. 2000-330015 discloses an objective lens for endoscopes constituted by two lens groups, in which a lens group toward the image side moves toward the image side and toward the object side to focus on distant objects and close objects, respectively.
Meanwhile, recently, images which are obtained by endoscopes are converted into electrical signals and image processes are administered thereon, in order to observe blood vessels, surface structures, and the like. There are cases in which a short wavelength laser beam is employed as a light source in addition to a white light source. Objective lenses for endoscopes which are compatible with such light sources have also been proposed. For example, Japanese Unexamined Patent Publication No. 2011-227380 discloses an objective lens for endoscopes, in which aberrations are favorably corrected throughout a wide wavelength range from a short wavelength band that includes a wavelength of approximately 405 nm to a visible wavelength band.